This invention lies in the field of moderately small air conditioning systems of the size of from 5 to 10 tons cooling capacity. It is used in buildings in which there is preferably a flat roof immediately above a living or working area, although the apparatus of this invention is adaptable to pitched roofs. In the prior art it was necessary to mount the air conditioning unit on the roof at the appropriate time during the construction of the building, after the deck was in place, and before the roof covering was installed. It was not always possible to have the electrical conduits in place or the various facilities required for the complete connection of the air conditioning system. This caused inefficiency and delay in the installation of the air conditioning equipment.